1. Field of the Invention
This invention relates to an oculo-perimetric device, otherwise known as a perimeter, and more particularly to a perimeter that projects a target spot onto the inside surface of a visual field dome and records the position of the projected target spot and a patient""s responses relating to the visual recognition thereof.
2. Description of the Prior Art
Measuring a patient""s visual field is an effective way of diagnosing some eye ailments. The Goldmann perimeter is extensively employed for such measurements. In a conventional Goldmann perimeter, a target spot is projected onto a hemispherical visual field dome of the perimeter, and an examiner manually adjusts the projection position of the spot by a means of a purely mechanical mechanism. The responses of the patient to the target spot are then recorded on a chart.
In addition to manual Goldmann perimeters, in recent years there has come into use automatic perimeters in which the control of the target is automated. In an automatic perimeter, the target projection mechanism is controlled in accordance with a predetermined program, or multiple LEDs or other such light sources are disposed which are lit in accordance with the program, and the patient operates a response button when given a suitable prompt.
A factor behind the emergence of the automated perimeter was that manual perimeters were difficult to use because the target had to be operated manually.
FIGS. 4 and 5 show the arrangement for a conventional manual Goldmann perimeter. In FIGS. 4 and 5, reference numeral 202 shows a visual field dome, in front of which a patient chin-rest 203 is positioned at the dome center. Over the dome 202 is a light source 211. To examine a patient""s visual field, a projector 212 is used to project a target spot from the light source 211 at any point on the inside surface of the dome 202, and the patient""s responses to the targets are recorded on a chart. The patient responds by pressing a push-button 213, which is located on the stand used to support the dome 202.
FIG. 5 is a rear view of the perimeter. As shown, at the center of the dome 202 there is a telescope 204 that is used to align the patient""s eye with the perimeter and to monitor the examination sequences. The projector 212 is operated by a mechanical linkage comprising a pantograph 210a connected to the projector. At the end of the pantograph 210a, there is a handle 210. During the examination, a pen attached to the handle 210 records the positions of the target spot and the positions of the patient""s responses on a printed paper 206 that is mounted at the back of the perimeter. An appropriate chart for isoptometry is printed on the recording pager for each system employed.
Because the target spot is operated and recorded by purely mechanical means in the case of a manual Goldmann perimeter, the measurement and recording operations require skill and experience. Moreover, during the examination the posture of the examiner is constrained, imposing a considerable burden on the examiner.
In an automatic perimeter the control of the target movement is automated according to a program. Although this simplifies the measurement operation, the use of a pre-programmed measurement sequence makes it impossible to change the measurement points to match a patient""s particular situation, making it impossible to perform measurements with good efficiency. Another problem is the length of time it takes to perform the measurements. Manual Goldmann perimeters do not have the above problems of the automated perimeter, so the Goldmann perimeter had some advantages that were worth looking at.
It is therefore an object of the invention to solve such problems and provide a perimeter that has the advantages of both a manual Goldmann perimeter and an automatic perimeter, and can be manually operated with a degree of freedom and enables measurements to be performed readily and efficiently in accordance with the examiner""s intentions.
In accordance with the present invention, the above object is attained by a perimeter that projects a target spot onto the inside surface of a visual field dome and records the position of the projected target spot and patient""s responses relating to the visual recognition thereof, comprising an optical projection system for projecting the target spot on the inside surface of the visual field dome; control means including semi-automatic control means for electronically controlling the optical projection system to project the target spot onto only user-selected positions; input means used for entry of the user-selected positions for control of the projection position of the target spot by the control means and for recording of response information relating to the patient""s response; and display means for displaying the user-selected positions control information and response information supplied via the input means, the display means having an input surface for entry of the user-selected positions and response information by the input means.